Brought more flexibility to redirect methods.

I had a use case where I needed to override entire `deleteAction()` in order to redirect to:

```php
 return $this->redirectToRoute(
    $this->getRedirectRoute('show'),
    array('id' => $resource->getParent()->getId())
);
```

Instead to collection. So I passed `resource` to `redirectToCollection()` to prevent this case.

Also, I found `redirectToReferer()` usable. I used it in my `moveUpAction()` and `moveDownAction()`.

Makes sense?